#include <iostream>
#include <vector>
using namespace std;
class Solution {
public:
    int peakIndexInMountainArray(vector<int>& arr) {
        int n = arr.size();
        int ans = -1;
        for (int i = 1; i < n - 1; ++i) {
            if (arr[i] > arr[i + 1]) {
                ans = i;
                break;
            }
        }
        return ans;
    }
};
int main()
{
	return 0;
}